DTV receiver and method of processing broadcast signal in DTV receiver

ABSTRACT

A DTV receiver includes a tuner, a demodulator, a known sequence detector, and a frequency domain equalizer. The tuner initially receives a broadcast signal including valid data in which a known data sequence is periodically repeated. The demodulator demodulates the broadcast signal, and the known sequence detector detects the known data sequence from the demodulated signal. The frequency domain equalizer compensates channel distortion of the demodulated broadcast signal in a frequency domain using the detected known data sequence. In addition, the DTV receiver may further include a time domain equalizer which compensates channel distortion of the time domain signal, or a noise canceller which removes a predicted noise from the time domain signal.

This application is a continuation of U.S. application Ser. No.11/613,923, filed on Dec. 20, 2006 (now U.S. Pat. No. 8,050,316), whichclaims the benefit of Korean Patent Application No. 10-2005-0126484,filed on Dec. 20, 2005, and U.S. Provisional Application No. 60/867,457,filed on Nov. 28, 2006, which are all hereby incorporated by referenceherein in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital broadcasting system, and moreparticularly, to a DTV receiver and a method of processing a broadcastsignal in a DTV receiver that are used for receiving a digital broadcastsignal.

2. Discussion of the Related Art

The VSB transmission mode, which is adopted as the standard for digitalbroadcasting in North America and the Republic of Korea, is a systemthat has been developed for the transmission of MPEG video/audio data.However, presently, the technology for processing digital signals isbeing developed at a vast rate, and, as a larger number of thepopulation uses the Internet, digital electric appliances, computers,and the Internet are being integrated. Therefore, in order to meet withthe various requirements of the users, a system that can transmitvideo/audio data as well as other diverse supplemental informationthrough a digital television channel needs to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the MPEG video/audio data. However,with the advent of digital broadcasting, ATSC VSB digital televisionreceivers that receive only MPEG video/audio data are already suppliedto the market. Therefore, the supplemental data that are transmittedthrough the same channel as the MPEG video/audio data should notinfluence the conventional ATSC VSB receivers that are provided in themarket. In other words, this may be defined as ATSC VSB compatibility,and the supplemental data broadcast system should be compatible with theATSC VSB system. Herein, the supplemental data may also be referred toas enhanced data or EVSB data. Furthermore, in a poor channelenvironment, the receiving performance of the conventional ATSC VSBreceiving system may be deteriorated. More specifically, resistance tochanges in channels and noise is more highly required when usingportable and/or mobile receivers.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a DTV receiver and amethod of processing a broadcast signal in a DTV receiver thatsubstantially obviate one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a DTV receiver and amethod of processing broadcast signal in a DTV receiver that is suitablefor transmitting supplemental data and that is highly resistant tonoise.

Another object of the present invention is to provide a DTV transmitterand a method of processing broadcast signal in a DTV transmitter thatcan regularly insert known data in a specific domain of the supplementaldata and transmitting the data to a DTV receiver, thereby enhancing thereceiving performance of the DTV receiver.

A further object of the present invention is to provide a DTVtransmitter and a method of processing broadcast signal in a DTVtransmitter that can use the regularly inserted and transmitted knowndata in order to enhance channel equalization performance.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adigital television (DTV) receiver includes a tuner, a demodulator, aknown sequence detector, and a frequency domain equalizer. The tunerinitially receives a broadcast signal including valid data (main and/orenhanced data) in which a known data sequence is periodically repeated.The demodulator demodulates the broadcast signal by performing at leastone of carrier and time recovery. The known sequence detector detectsthe known data sequence from the signal outputted from the tuner ordemodulator. The frequency domain equalizer compensates channeldistortion of the demodulated broadcast signal in a frequency domainusing the known data sequence detected by the known sequence detector.

The frequency domain equalizer includes a first transformer, a channelestimator, a second transformer, a coefficient calculator, acompensator, and a third transformer. The first transformer converts thedemodulated broadcast signal into first frequency domain data. Thechannel estimator estimates a channel impulse response of thedemodulated signal using the detected known data sequence, and thesecond transformer converts the estimated channel impulse response intosecond frequency domain data. The coefficient calculator calculatesequalization coefficients using the second frequency domain data. Thecompensator compensates channel distortion of the first frequency domaindata by multiplying the first frequency data with the equalizationcoefficients. The third transformer finally converts the first frequencydomain data compensated by the compensator into a time domain signal.

In addition, the DTV receiver according to the present invention mayfurther include a time domain equalizer for compensating channeldistortion of the time domain signal. The time domain equalizer mayinclude a decision unit, a feedback filter, and an adder. The decisionunit generates a decision value which is the closest reference signallevel to an output of the time domain equalizer. The feedback filterperforms feedback filtering on the decision value, the adder adds thefiltered decision value to the time domain signal to compensate thechannel distortion of the time domain signal.

Furthermore, the DTV receiver may further include a noise canceller forremoving a noise from the time domain signal. It may include a decisionunit, a noise predictor, and a subtracter. The decision unit generates adecision value which is the closest reference signal to an output of thenoise canceller. The noise predictor generates a predicted noise basedon the time domain signal outputted from the third transmitter and thedecision value. The subtracter subtracts the predicted noise from thetime domain signal.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block view of a digital broadcast transmittingsystem according to the present invention;

FIG. 2 illustrates an example of a data structure having known dataregularly inserted in valid data according to the present invention;

FIG. 3( a) to FIG. 3( c) illustrate correlations between a main signaland a ghost signal when a post-ghost exists;

FIG. 4( a) to FIG. 4( c) illustrate correlations between a main signaland a ghost signal when a pre-ghost exists;

FIG. 5 illustrates a block view of a channel equalization deviceaccording to a first embodiment of the present invention;

FIG. 6 illustrates a block view of a channel equalization deviceaccording to a second embodiment of the present invention;

FIG. 7 illustrates a block view of a channel equalization deviceaccording to a third embodiment of the present invention;

FIG. 8 illustrates a block view of a demodulating unit having thechannel equalization device according to the present invention appliedtherein;

FIG. 9 illustrates a block view showing the structure of a digitalbroadcast (or television) receiver according to an embodiment of thepresent invention; and

FIG. 10 illustrates a block view showing the structure of a digitalbroadcast (or television) receiver according to another embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In addition, although the terms used in the present invention areselected from generally known and used terms, some of the termsmentioned in the description of the present invention have been selectedby the applicant at his or her discretion, the detailed meanings ofwhich are described in relevant parts of the description herein.Furthermore, it is required that the present invention is understood,not simply by the actual terms used but by the meaning of each termlying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, weather forecast, and so on, or consist of video/audiodata. Additionally, the known data refer to data already known basedupon a pre-determined agreement between the transmitter and thereceiver. Furthermore, the main data consist of data that can bereceived from the conventional receiving system, wherein the main datainclude video/audio data.

The present invention relates to regularly inserting known data in aspecific domain of a data packet and transmitting the processed datapacket and to using the regularly inserted and transmitted known datafor channel equalization, thereby enhancing the equalizing performance.

FIG. 1 illustrates an example of a digital broadcast transmitting systemfor regularly inserting and transmitting known data. The digitalbroadcast transmitting system shown in FIG. 1 is only exemplary for thedescription of the present invention. In other words, any type oftransmitter that can regularly insert and transmit a known data sequencemay be used in the present invention, and the type of transmitter is notlimited to the example shown in FIG. 1. Referring to FIG. 1, the digitalbroadcast transmitting system includes an E-VSB pre-processor 101, anE-VSB packet formatter 102, a packet multiplexer 103, a data randomizer104, a scheduler 105, a Reed-Solomon (RS) encoder and parity placeholder inserter 106, a data interleaver 107, a byte-symbol converter108, an E-VSB symbol processor 109, a known data generator 110, asymbol-byte converter 111, a non-systematic RS encoder 112, a trellisencoder 113, a frame multiplexer 114, and a transmitter 120.

In the present invention having the above-described structure, a maindata packet is outputted to the packet multiplexer 103 in transportstream (TS) packet units, and enhanced data are outputted to the E-VSBpre-processor 101. The E-VSB pre-processor 101 pre-processes theenhanced data, such as encoding additional error correction,interleaving, and expanding data bytes by inserting null data, and thenoutputs the pre-processed enhanced data to the E-VSB packet formatter102. Based upon the control of the scheduler 105, the E-VSB packetformatter 102 multiplexes the pre-processed enhanced data and a knowndata place holder having the null data inserted therein, therebyconfiguring a group. The data within the group are then divided into184-byte unit enhanced data packets, and a 4-byte MPEG header is addedto the beginning of the enhanced data packet, thereby outputting a188-byte enhanced data packet (i.e., a MPEG compatibility packet).

Herein, the E-VSB packet formatter 102 decides the known data placeholder so that, when a receiving end (or receiver) receives the knowndata in accordance with the control of the scheduler 105, a known datasequence having the same length as the received known data can bereceived regularly. The output of the E-VSB packet formatter 102 isinputted to the packet multiplexer 103. The packet multiplexer 103time-division multiplexes the main data packet and the enhanced datapacket group in transport stream (TS) packet units and outputs themultiplexed TS packet in accordance with the control of the scheduler105. More specifically, the scheduler 105 generates and outputs acontrol signal so that the packet formatter 102 can multiplex theenhanced data and the known data place holder.

The output of the packet multiplexer 103 is inputted to the datarandomizer 104. The data randomizer 104 discards (or deletes) the MPEGsynchronization data byte and randomizes the remaining 187 bytes byusing uses a pseudo random byte that is generated by the data randomizer104. Thereafter, the processed data are inputted to the RSencoder/parity place holder inserter 106. Herein, when the randomizeddata correspond to the main data packet, the RS encoder/parity placeholder inserter 106 performs a systematic RS coding process.Alternatively, when the randomized data correspond to the enhanced datapacket, the RS encoder/parity place holder inserter 106 performs anon-systematic RS parity place holder insertion process. The output ofthe RS encoder/parity place holder inserter 106 is inputted to the datainterleaver 107. Subsequently, the data interleaver 107 receives theprocessed data, which are then interleaved and outputted. At this point,the data interleaver 107 receives a RS parity byte that has been newlycalculated and outputted by the non-systematic RS encoder. Herein, thenewly received RS parity byte is outputted instead of the non-systematicRS parity place holder which has not yet been outputted.

One byte outputted from the data interleaver 107 is converted to foursymbols by the byte-symbol converter 108, which are then outputted tothe E-VSB symbol processor 109. Herein, one symbol is configured of twobits. Furthermore, the known data generated from the known datagenerator 110 are also outputted to the E-VSB symbol processor 109.Herein, the known data generated from a symbol domain correspond toknown data symbols. Since the receiver uses the known data in the symboldomain, it is more effective to generate a known data symbol sequencehaving the characteristics desired by the symbol domain.

Meanwhile, when the data being inputted to the E-VSB symbol processor109 correspond to the known data place holder that has been converted tosymbols by the byte-symbol converter 108, the known data place holder isreplaced with the known data generated from the known data generator110. Additionally, a data symbol is generated and outputted at thebeginning of the known data sequence, so that the memory of the trellisencoder 113 can be initialized to a pre-decided status. In order to doso, a value of the memory included in the trellis encoder 113 should bereceived from the E-VSB symbol processor 109.

The memory value of the trellis encoder 113 may also be used inadditional signal processing for the enhanced data symbols. Also, thememory of the trellis encoder 113 is initialized at the beginning of theknown data sequence because a wide range of output sequences may beoutputted in accordance with the memory status of the trellis encoder113 even though the known data sequence is inputted to the trellisencoder 113. Therefore, the memory status of the trellis encoder 113 isfirst initialized to a pre-decided value. Subsequently, when the knowndata are inputted, a known data output sequence may also be obtainedfrom the output of the trellis encoder 113.

The output symbols of the E-VSB symbol processor 109 are inputted to thetrellis encoder 113, and the symbol are then trellis-encoded. Thetrellis encoder 113 pre-codes the data being inputted as the upper bitof the symbols outputted from the E-VSB symbol processor 109. Thetrellis encoder 113 also trellis-encodes the data being inputted as thelower bit of the symbols outputted from the E-VSB symbol processor 109.Then, the trellis encoder 113 outputs the processed data to the framemultiplexer 114. Meanwhile, since the E-VSB symbol processor 109receives and processes the symbols each configured of two bits and thenoutputs the processed symbol, which is also configured of two bits, thesymbol-byte converter 111 should convert the received symbols to onebyte. This is to allow the non-systematic RS encoder 112 to recalculatethe RS parity from the output of the E-VSB symbol processor 109. Morespecifically, the symbol-byte converter 111 converts the input symbolsto byte unit data, which are then outputted to the non-systematic RSencoder 112.

The non-systematic RS encoder 112 calculates 20 bytes of RS parity forthe enhanced data packet configured of 187 data bytes. Thereafter, thenon-systematic RS encoder 112 outputs the calculated RS parity to thedata interleaver 107. The data interleaver 107 receives the RS paritybytes calculated and outputted by the non-systematic RS encoder 112.Then, the received RS parity bytes are outputted instead of thenon-systematic RS parity place holders, which have not yet beenoutputted. The non-systematic RS-coding process is performed because theenhanced data symbols and the known data place holders have been changedto different values by the E-VSB symbol processor 109. This is toprevent any decoding error from occurring, when the RS-decoding processis performed by the conventional ATSC VSB receiver. In other words, thisis to provide backward compatibility with the conventional ATSC VSBreceiver.

Meanwhile, the non-systematic RS encoder 112 receives the output of theknown data generator 110 so that the non-systematic RS encoder 112 canreceive in advance the known data that are outputted later than the RSparity bytes from the symbol-byte converter 111. The frame multiplexer114 inserts 4 segment synchronization symbols after each output symbolof the trellis encoder 113, so as to configure a data segment of 832symbols. Also, the frame multiplexer 114 inserts one fieldsynchronization symbol after each 312 data segment, so as to configure adata field. Then, the frame multiplexer 114 outputs the newly configureddata segment and data field to the transmitter 120. The transmitter 120inserts a pilot signal in the output of the frame multiplexer 114 havingthe segment synchronization signal and the field synchronization signalinserted therein. Then, the processed data are VSB modulated andconverted to radio frequency (RF) signals, which are then transmittedthrough an antenna. In order to do so, the transmitter 120 includes apilot inserter 121, a VSB modulator 122, and a RF-up converter 123.Herein, a pre-equalizer filter may be optionally included.

As described above, the digital broadcast transmitting system accordingto the present invention may regularly insert known data in a VSB dataframe. FIG. 2 illustrates an exemplary a data structure of a VSB signalthat regularly inserts and transmits known data sequences having thesame pattern in between actual data. Referring to FIG. 2, M representsthe number of known data symbols, and N represents the number of symbolscorresponding to valid data. Therefore, for each (M+N) symbol cycle, Mnumber of known data symbols are inserted and transmitted. Herein, N maycorrespond to one of enhanced data, main data, and a combination ofenhanced data and main data. In the present invention, in order to bedifferentiated with the known data, N will be referred to as valid datafor simplicity.

Accordingly, when the known data are regularly inserted in the validdata as described above, the channel equalizer included in the digitalbroadcast receiver used the inserted known data as a training sequence,so as to be used either for an accurate decision value or for estimatingan impulse response of a channel. Meanwhile, when the same known dataare regularly inserted, the known data interval may be used as a guardinterval in a frequency domain channel equalizer according to thepresent invention. The guard interval prevents interference that occursbetween blocks due to a multiple path channel. This is because the knowndata of the known data section located behind the data blockcorresponding to the (M+N) symbol may be considered as being copied infront of the data block corresponding to the (M+N) symbol, as shown inFIG. 2.

The above-described structure is referred to as a cyclic prefix. Thisstructure provides circular convolution to an impulse response in a timedomain between a data block transmitted from the digital broadcasttransmitting system and a channel. Accordingly, this facilitates thechannel equalizer of a digital broadcast receiving system to performchannel equalization in a frequency domain by using a fast fouriertransform (FFT) and an inverse fast fourier transform (IFFT). Morespecifically, when viewed in the frequency domain, the data blockreceived by the receiving system is expressed as a multiplication of thedata block and the channel impulse response. Therefore, when performingthe channel equalization, by multiplying the inverse of the channel inthe frequency domain, the channel equalization may be performed moreeasily.

FIG. 3 and FIG. 4 illustrate examples of the known data section actingas a guard section in a multiple path channel environment, therebypreventing interference in adjacent (or neighboring) blocks. Referringto FIG. 3 and FIG. 4, the path having the largest amount of energy willbe referred to as a main path for simplicity. Herein, as shown in FIG.3( a), a ghost being received after the main path is defined as apost-ghost. Alternatively, as shown in FIG. 4( a), a ghost beingreceived before the main path is defined as a pre-ghost. Referring tothe drawings, assuming that both the post-ghost and the pre-ghost exist,the FFT block which corresponds to a section performing FFT operationsis set to have a guard section located both in front of and behind thevalid data. Herein, the known data located in front of the valid datawithin the FFT block is referred to as M2, and the known data locatedbehind the valid data within the FFT block is referred to as M1.

FIG. 3 illustrates correlations between a main signal and a ghost signalwhen a post-ghost exists. More specifically, FIG. 3( b) illustrates anexample of a main signal, and FIG. 3( c) illustrates an example of thepost-ghost signal. Referring to FIG. 3, when a time difference betweenthe main signal and a ghost is t0, and when t0 is smaller than M2, theknown data pattern that is regularly transmitted is identical.Therefore, signal B which is added to the main signal within the FFTblock by the ghost corresponds to the same data as the end portion A ofthe main signal. More specifically, since a signal having a circularlyshifted data block is added to the current data block of the main signalwithin the FFT block, interference from an adjacent data block may beprevented. In other words, the effect (or influence) of the ghost isshown in a circular convolution form within the time domain of the mainsignal and an impulse response of a channel.

FIG. 4 illustrates correlations between a main signal and a ghost signalwhen a pre-ghost exists. More specifically, FIG. 4( b) illustrates anexample of a main signal, and FIG. 4( c) illustrates an example of thepre-ghost signal. Referring to FIG. 4, which is similar to the exampleof the post-ghost shown in FIG. 3, when the time difference t0 betweenthe main signal and the ghost is smaller than M1, the effect (orinfluence) of the ghost is shown in a circular convolution form of themain signal and the impulse response of a channel.

As described above, when the time difference between the main signal andthe pre-ghost is smaller than the M1 symbol time, or when the timedifference between the main signal and the post-ghost is smaller thanthe M2 symbol time, the effect of the ghost is shown within the FFTblock in a circular convolution form. More specifically, when a delayspread of a multiple path (or ghost) is smaller than the guard section,the effect of the multiple path becomes a circular convolution form ofthe valid data block (or FFT block) and the channel impulse responsewithin the time domain. Accordingly, in the frequency domain, the effectof the multiple path is shown as a multiplication of the data block andthe channel impulse response. Therefore, by using such characteristicschannel equalization may be easily performed in the frequency domain.Thus, the structure of the channel equalization may be simplified.

FIG. 5 illustrates a block view of an example of a frequency domainequalizer according to the present invention. The frequency domainequalizer includes a first fast fourier transform (FFT) unit 501, achannel estimator 502, a second FFT unit 503, a coefficient calculator504, a multiplier 505, and an inverse fast fourier transform (IFFT) unit506. More specifically, when a series of identical known data sequencesis regularly inserted in the valid data sequence and then transmitted,the first FFT unit 501 performs FFT by FFT block units on the receiveddata. Then, the first FFT unit 501 converts the processed data tofrequency domain data, which are then outputted to the multiplier 505.Herein, assuming that both post-ghost and pre-ghost exist, the FFT blocksection is set to have part of the known data corresponding to the knowndata section positioned both before (or in front of) and after (orbehind) the valid data.

The channel estimator 502 uses the data received during the known datasection and the known data, which are known by the receiver according toan agreement between the receiver and the transmitter, in order toestimate a channel. Then, the channel estimator 502 outputs theestimated channel to the second FFT unit 503. The known data section maybe known by a synchronization recovery process performed by asynchronization recovery unit (not shown) located before the channelequalization device. More specifically, the channel estimator 502performs the channel estimation process only during the known datasection. The channel estimator 502 estimates an impulse response of adiscrete equalization channel through which a signal transmitted fromthe transmitter is assumed to have passed during the known data section.Thereafter, the channel estimator 502 outputs the estimated result tothe second FFT unit 503.

The second FFT unit 503 performs a FFT process on the estimated channeland converts the processed channel to the frequency domain. Thereafter,the processed channel is outputted to the coefficient calculator 504.The coefficient calculator 504 uses the channel impulse response of thefrequency domain to calculate the equalizer coefficient and outputs thecalculated result to the multiplier 505. The multiplier 505 multipliesthe output of the coefficient calculator 504 and the output of the firstFFT unit 501 after each frequency bin and, then, outputs each multipliedresult to the IFFT unit 506. The IFFT unit 506 performs an IFFT processof the output (or result) of the multiplier 505, thereby converting themultiplied result to a time domain signal.

The coefficient calculator 504 of FIG. 5 may calculate the equalizercoefficient by using a zero forcing method, which simply calculates theinverse of a channel. Alternatively, the coefficient calculator 504 mayalso calculate the equalizer coefficient by using a minimum mean squarederror (MMSE) method, which estimates the amount of noise in the channelso as to minimize a mean squared error corresponding to the output ofthe equalizer. As shown in FIG. 5, when equalization is performed in thefrequency domain, the distortion of data caused by a multiple path maybe compensated. However, a white noise element that is added to theoutput of the multiple path channel is amplified by the frequency domainequalizer, thereby changing to a colored noise. By removing the colorednoise that has been amplified as described above, the equalizationperformance of the frequency domain channel equalizer may be enhanced.

FIG. 6 and FIG. 7 illustrate exemplary structures of a channel equalizerthat is used for resolving noise amplification problems caused by thefrequency domain equalizer as described above. FIG. 6 illustrates ablock view showing the channel equalization device having a time domainequalizer 510 added to the frequency domain equalizer shown in FIG. 5.Herein, the time domain equalizer 510 includes an adder 511, a decisiondevice 512, and a feedback filter 513. More specifically, the data thatare equalized by the frequency domain equalizer 500 and converted totime domain data, as shown in FIG. 5, are inputted to the adder 511 ofthe time domain equalizer 510. The adder 511 then adds the output of thefrequency domain equalizer 500 and the output of the feedback filter513. Thereafter, the added result is outputted for data recovery andsimultaneously outputted to the decision device 512.

The decision device 512 compares the output signal outputted from adder511 with a predetermined reference signal level. Accordingly, thereference signal level that is the nearest to the output signal of theadder 511 is decided and outputted as the decision value. Subsequently,the feedback filter 513 receives the decision value of the decisiondevice 512, so as to perform a filtering process in the time domain.Then, the processed decision value is outputted to the adder 511. Atthis point, if the decision is accurately made by the decision device512, since the decision value having the noise removed from the outputelement of the frequency domain equalizer 500 is re-inputted as theinput of the feedback filter 513, amplification of the noise does notoccur. Therefore, the equalization performance is more excellent thanthe frequency domain equalizer 500 of FIG. 5.

FIG. 7 illustrates a block view showing the channel equalization devicehaving a noise remover 520 added to the frequency domain equalizer 500shown in FIG. 5. Herein, the noise remover 520 includes a subtracter701, a decision device 522, and a noise predictor 523. Morespecifically, the data that have been equalized by the frequency domainchannel equalizer 500 shown in. FIG. 5 and converted to time domain dataare inputted to the subtracter 521 of the noise remover 520. Thesubtracter 521 removes the noise, which is predicted by the noisepredictor 523, from the signal equalized in the frequency domain. Then,the signal having the amplified noise removed therefrom is outputted fordata recovery and simultaneously outputted to the decision device 522.

The decision device 522 outputs a decision value closest to the outputof the subtracter 521 to the noise predictor 523. The noise predictor523 removes the output of the decision device 522 from the signal thathas been converted to the time domain by the frequency domain equalizer500, so as to calculate the noise element. Thereafter, the calculatednoise element is used as an input of a filter within the noise predictor523. The noise predictor 523 uses the filter to predict the colorednoise element included in the output symbol of the current frequencydomain equalizer 500. Then, the predicted colored noise element isoutputted to the subtracter 521. Subsequently, the subtracter 521removes the noise element predicted by the noise predictor 523 from theoutput of the frequency domain equalizer 500, thereby outputting thefinal data.

FIG. 8 illustrates a block view of a demodulating unit having thechannel equalization device shown in FIG. 5 to FIG. 7 applied therein.The demodulating unit uses the known data information inserted in anenhanced data section and transmitted by the transmitting system, so asto restore the carrier wave synchronization, restore the framesynchronization, and perform channel equalization, thereby enhancing thereceiving performance of the present invention. The demodulating unitshown in FIG. 8 is merely exemplary and the scope of the presentinvention is not limited to the example set forth herein.

Referring to FIG. 8, the demodulating unit includes a VSB demodulator601, an equalizer 602, a known data detector 603, a Viterbi decoder 604,a data deinterleaver 605, a RS decoder/non-systematic RS parity remover606, and a derandomizer 607. The digital broadcast receiving systemfurther includes a main data packet remover 608, an E-VSB packetdeformatter 609, and an E-VSB data processor 610.

More specifically, the received data through a tuner inputs to the VSBdemodulator 601 and the known data detector 603. The VSB demodulatordemodulates the tuned channel frequency so as to perform carrier waverecovery and timing recovery, thereby creating a baseband signal. Then,the VSB demodulator 601 outputs the created baseband signal to theequalizer 602 and the known data detector 603. The equalizer 602 usesthe channel equalization device shown in FIG. 5 to FIG. 7 so as tocompensate for any channel distortion included in the demodulatedsignal. Thereafter, the equalizer 602 outputs the processed signal tothe Viterbi decoder 604.

At this point, the known data detector 603 detects the known data symbolsequence inserted from the transmitter from the input/output data of theVSB demodulator 601 (i.e., the data prior to demodulation or the dataafter demodulation). Then, the known data detector 603 outputs thedetected sequence to the VSB demodulator 601 and the equalizer 602. Whenthe VSB demodulator 601 uses the known data symbol sequence during thetiming recovery or the carrier wave recovery, the demodulatingperformance may be enhanced. Similarly, when the equalizer 602 uses theknown data symbol sequence, the equalization performance may beenhanced.

The Viterbi decoder 604 Viterbi-decodes the main symbol and the enhanceddata symbol outputted from the equalizer 602, so as to convert thesymbols into data bytes, thereby outputting the newly converted databytes to the deinterleaver 605. The 8-level value decided by the Viterbidecoder 604 is provided to the equalizer 602 so as to enhance theequalization performance. The deinterleaver 605 performs the inverseoperation of the data interleaver of the transmitting system and, then,outputs the processed data to the RS decoder/non-systematic RS parityremover 606. If the received packet is the main data packet, the RSdecoder/non-systematic RS parity remover 606 RS-decodes the receivedpacket. Alternatively, if the received packet is the enhanced datapacket, the RS decoder/non-systematic RS parity remover 606 removes thenon-systematic RS parity byte from the received packet. Thereafter, theprocessed packet is outputted to the derandomizer 607.

The derandomizer 607 performs an inverse process of the randomizer so asto process the output of the RS decoder/non-systematic RS parity remover606. Subsequently, the derandomizer 607 inserts a MPEG synchronizationdata byte at the beginning of each packet and outputs the processedpacket in 188-byte units. The output of the derandomizer 607 isoutputted to the main MPEG decoder (not shown) and to the main datapacket remover 608 at the same time.

Meanwhile, the main data packet remover 608 removes the 188-byte unitmain data packet from the data outputted from the derandomizer 607 andoutputs the processed data to the E-VSB packet deformatter 609.Subsequently, the E-VSB packet deformatter 609 removes (or discards) the4-byte MPEG header byte and the known data byte that have been insertedby the E-VSB packet formatter of the transmitting system, and alsoremoves the null bit or repetition bit that has been inserted for thebyte expansion from the processed data. Thereafter, the E-VSB packetdeformatter 609 outputs the processed data to the E-VSB data processor610. The E-VSB data processor 610 performs an inverse process of theE-VSB pre-processor 101 of the transmitting system, so as to process thedata outputted from the E-VSB packet deformatter 609. Subsequently, theE-VSB data processor 610 outputs the final output data.

FIG. 9 illustrates a block view showing the structure of a digitalbroadcast receiver according to an embodiment of the present invention.Referring to FIG. 9, the digital broadcast receiver includes a tuner701, a demodulating unit 702, a demultiplexer 703, an audio decoder 704,a video decoder 705, a native TV application manager 706, a channelmanager 707, a channel map 708, a first memory 709, a data decoder 710,a second memory 711, a system manager 712, a data broadcastingapplication manager 713, a storage controller 714, and a third memory715. Herein, the third memory 715 is a mass storage device, such as ahard disk drive (HDD) or a memory chip. The tuner 701 tunes a frequencyof a specific channel through any one of an antenna, cable, andsatellite. Then, the tuner 701 down-converts the tuned frequency to anintermediate frequency (IF), which is then outputted to the demodulatingunit 702. At this point, the tuner 701 is controlled by the channelmanager 707. Additionally, the result and strength of the broadcastsignal of the tuned channel are also reported to the channel manager707. The data that are being received by the frequency of the tunedspecific channel include main data, enhanced data, and table data fordecoding the main data and enhanced data.

In the embodiment of the present invention, examples of the enhanceddata may include data provided for data service, such as Javaapplication data, HTML application data, XML data, and so on. The dataprovided for such data services may correspond either to a Java classfile for the Java application, or to a directory file designatingpositions (or locations) of such files. Furthermore, such data may alsocorrespond to an audio file and/or a video file used in eachapplication. The data services may include weather forecast services,traffic information services, stock information services, servicesproviding information quiz programs providing audience participationservices, real time poll, user interactive education programs, gamingservices, services providing information on soap opera (or TV series)synopsis, characters, original sound track, filing sites, servicesproviding information on past sports matches, profiles andaccomplishments of sports players, product information and productordering services, services providing information on broadcast programsby media type, airing time, subject, and so on. The types of dataservices described above are only exemplary and are not limited only tothe examples given herein. Furthermore, depending upon the embodiment ofthe present invention, the enhanced data may correspond to meta data.For example, the meta data use the XML application so as to betransmitted through a DSM-CC protocol.

The demodulating unit 702 performs VSB-demodulation and channelequalization on the signal being outputted from the tuner 701, therebyidentifying the main data and the enhanced data. Thereafter, theidentified main data and enhanced data are outputted in TS packet units.An example of the demodulating unit 702 is shown in FIG. 8. Thedemodulating unit shown in FIG. 8 is merely exemplary and the scope ofthe present invention is not limited to the example set forth herein. Inthe embodiment given as an example of the present invention, only theenhanced data packet outputted from the demodulating unit 702 isinputted to the demultiplexer 703. In this case, the main data packet isinputted to another demultiplexer (not shown) that processes main datapackets. Herein, the storage controller 714 is also connected to theother demultiplexer in order to store the main data after processing themain data packets. The demultiplexer of the present invention may alsobe designed to process both enhanced data packets and main data packetsin a single demultiplexer.

The storage controller 714 is interfaced with the demultiplexer so as tocontrol instant recording, reserved (or pre-programmed) recording, timeshift, and so on of the enhanced data and/or main data. For example,when one of instant recording, reserved (or pre-programmed) recording,and time shift is set and programmed in the receiving system (orreceiver) shown in FIG. 9, the corresponding enhanced data and/or maindata that are inputted to the demultiplexer are stored in the thirdmemory 715 in accordance with the control of the storage controller 714.The third memory 715 may be described as a temporary storage area and/ora permanent storage area. Herein, the temporary storage area is used forthe time shifting function, and the permanent storage area is used for apermanent storage of data according to the user's choice (or decision).

When the data stored in the third memory 715 need to be reproduced (orplayed), the storage controller 714 reads the corresponding data storedin the third memory 715 and outputs the read data to the correspondingdemultiplexer (e.g., the enhanced data are outputted to thedemultiplexer 703 shown in FIG. 9). At this point, according to theembodiment of the present invention, since the storage capacity of thethird memory 715 is limited, the compression encoded enhanced dataand/or main data that are being inputted are directly stored in thethird memory 715 without any modification for the efficiency of thestorage capacity. In this case, depending upon the reproduction (orreading) command, the data read from the third memory 715 pass throughthe demultiplexer so as to be inputted to the corresponding decoder,thereby being restored to the initial state.

The storage controller 714 may control the reproduction (or play),fast-forward, rewind, slow motion, instant replay functions of the datathat are already stored in the third memory 715 or presently beingbuffered. Herein, the instant replay function corresponds to repeatedlyviewing scenes that the viewer (or user) wishes to view once again. Theinstant replay function may be performed on stored data and also on datathat are currently being received in real time by associating theinstant replay function with the time shift function. If the data beinginputted correspond to the analog format, for example, if thetransmission mode is NTSC, PAL, and so on, the storage controller 714compression encodes the inputted data and stored the compression-encodeddata to the third memory 715. In order to do so, the storage controller714 may include an encoder, wherein the encoder may be embodied as oneof software, middleware, and hardware. Herein, an MPEG encoder may beused as the encoder according to an embodiment of the present invention.The encoder may also be provided outside of the storage controller 714.

Meanwhile, in order to prevent illegal duplication (or copies) of theinput data being stored in the third memory 715, the storage controller714 scrambles the input data and stores the scrambled data in the thirdmemory 715. Accordingly, the storage controller 714 may include ascramble algorithm for scrambling the data stored in the third memory715 and a descramble algorithm for descrambling the data read from thethird memory 715. Herein, the definition of scramble includesencryption, and the definition of descramble includes decryption. Thescramble method may include using an arbitrary key (e.g., control word)to modify a desired set of data, and also a method of mixing signals.

Meanwhile, the demultiplexer 703 receives the real-time data outputtedfrom the demodulating unit 702 or the data read from the third memory715 and demultiplexes the received data. In the example given in thepresent invention, the demultiplexer 703 performs demultiplexing on theenhanced data packet. Therefore, in the present invention, the receivingand processing of the enhanced data will be described in detail. Itshould also be noted that a detailed description of the processing ofthe main data will be omitted for simplicity starting from thedescription of the demultiplexer 703 and the subsequent elements.

The demultiplexer 703 demultiplexer enhanced data and program specificinformation/program and system information protocol (PSI/PSIP) tablesfrom the enhanced data packet inputted in accordance with the control ofthe data decoder 710. Thereafter, the demultiplexed enhanced data andPSI/PSIP tables are outputted to the data decoder 710 in a sectionformat. In order to extract the enhanced data from the channel throughwhich enhanced data are transmitted and to decode the extracted enhanceddata, system information is required. Such system information may alsobe referred to as service information. The system information mayinclude channel information, event information, etc. In the embodimentof the present invention, the PSI/PSIP tables are applied as the systeminformation. However, the present invention is not limited to theexample set forth herein. More specifically, regardless of the name, anyprotocol transmitting system information in a table format may beapplied in the present invention.

The PSI table is an MPEG-2 system standard defined for identifying thechannels and the programs. The PSIP table is an advanced televisionsystems committee (ATSC) standard that can identify the channels and theprograms. The PSI table may include a program association table (PAT), aconditional access table (CAT), a program map table (PMT), and a networkinformation table (NIT). Herein, the PAT corresponds to specialinformation that is transmitted by a data packet having a PID of ‘0’.The PAT transmits PID information of the PMT and PID information of theNIT corresponding to each program. The CAT transmits information on apaid broadcast system used by the transmitting system. The PMT transmitsPID information of a transport stream (TS) packet, in which programidentification numbers and individual bit sequences of video and audiodata configuring the corresponding program are transmitted, and the PIDinformation, in which PCR is transmitted. The NIT transmits informationof the actual transmission network.

The PSIP table may include a virtual channel table (VCT), a system timetable (STT), a rating region table (RRT), an extended text table (ETT),a direct channel change table (DCCT), an event information table (EIT),and a master guide table (MGT). The VCT transmits information on virtualchannels, such as channel information for selecting channels andinformation such as packet identification (PID) numbers for receivingthe audio and/or video data. More specifically, when the VCT is parsed,the PID of the audio/video data of the broadcast program may be known.Herein, the corresponding audio/video data are transmitted within thechannel along with the channel name and the channel number. The STTtransmits information on the current data and timing information. TheRRT transmits information on region and consultation organs for programratings. The ETT transmits additional description of a specific channeland broadcast program. The ETT transmits information on virtual channelevents (e.g., program title, program start time, etc.). The DCCT/DCCSCTtransmits information associated with automatic (or direct) channelchange. And, the MGT transmits the versions and PID information of theabove-mentioned tables included in the PSIP.

Each of the above-described tables included in the PSI/PSIP isconfigured of a basic unit referred to as a “section”, and a combinationof one or more sections forms a table. For example, the VCT may bedivided into 256 sections. Herein, one section may include a pluralityof virtual channel information. However, a single set of virtual channelinformation is not divided into two or more sections. At this point, thereceiving system may parse and decode the data for the data service thatare transmitting by using only the tables included in the PSI, or onlythe tables included in the PISP, or a combination of tables included inboth the PSI and the PSIP. In order to parse and decode the data for thedata service, at least one of the PAT and PMT included in the PSI, andthe VCT included in the PSIP is required. For example, the PAT mayinclude the system information for transmitting the data correspondingto the data service, and the PID of the PMT corresponding to the dataservice data (or program number). The PMT may include the PID of the TSpacket used for transmitting the data service data. The VCT may includeinformation on the virtual channel for transmitting the data servicedata, and the PID of the TS packet for transmitting the data servicedata.

Meanwhile, depending upon the embodiment of the present invention, aDVB-SI may be applied instead of the PSIP. The DVB-SI may include anetwork information table (NIT), a service description table (SDT), anevent information table (EIT), and a time and data table (TDT). TheDVB-SI may be used in combination with the above-described PSI. Herein,the NIT divides the services corresponding to particular networkproviders by specific groups. The NIT includes all tuning informationthat are used during the IRD set-up. The NIT may be used for informingor notifying any change in the tuning information. The SDT includes theservice name and different parameters associated with each servicecorresponding to a particular MPEG multiplex. The EIT is used fortransmitting information associated with all events occurring in theMPEG multiplex. The EIT includes information on the current transmissionand also includes information selectively containing differenttransmission streams that may be received by the IRD. And, the TDT isused for updating the clock included in the IRD.

Furthermore, three selective SI tables (i.e., a bouquet associate table(BAT), a running status table (RST), and a stuffing table (ST)) may alsobe included. More specifically, the bouquet associate table (BAT)provides a service grouping method enabling the IRD to provide servicesto the viewers. Each specific service may belong to at least one‘bouquet’ unit. A running status table (RST) section is used forpromptly and instantly updating at least one event execution status. Theexecution status section is transmitted only once at the changing pointof the event status. Other SI tables are generally transmitted severaltimes. The stuffing table (ST) may be used for replacing or discarding asubsidiary table or the entire SI tables.

In the present invention, the enhanced data included in the payloadwithin the TS packet consist of a digital storage media-command andcontrol (DSM-CC) section format. However, the TS packet including thedata service data may correspond either to a packetized elementarystream (PES) type or to a section type. More specifically, either thePES type data service data configure the TS packet, or the section typedata service data configure the TS packet. The TS packet configured ofthe section type data will be given as the example of the presentinvention. At this point, the data service data are includes in thedigital storage media-command and control (DSM-CC) section. Herein, theDSM-CC section is then configured of a 188-byte unit TS packet.

Furthermore, the packet identification of the TS packet configuring theDSM-CC section is included in a data service table (DST). Whentransmitting the DST, ‘0x95’ is assigned as the value of a stream_typefield included in the service location descriptor of the PMT or the VCT.More specifically, when the PMT or VCT stream_type field value is‘0x95’, the receiving system may acknowledge that data broadcastingincluding enhanced data (i.e., the enhanced data) is being received. Atthis point, the enhanced data may be transmitted by a data carouselmethod. The data carousel method corresponds to repeatedly transmittingidentical data on a regular basis.

At this point, according to the control of the data decoder 710, thedemultiplexer 703 performs section filtering, thereby discardingrepetitive sections and outputting only the non-repetitive sections tothe data decoder 710. The demultiplexer 703 may also output only thesections configuring desired tables (e.g., VCT) to the data decoder 710by section filtering. Herein, the VCT may include a specific descriptorfor the enhanced data. However, the present invention does not excludethe possibilities of the enhanced data being included in other tables,such as the PMT. The section filtering method may include a method ofverifying the PID of a table defined by the MGT, such as the VCT, priorto performing the section filtering process. Alternatively, the sectionfiltering method may also include a method of directly performing thesection filtering process without verifying the MGT, when the VCTincludes a fixed PID (i.e., a base PID). At this point, thedemultiplexer 703 performs the section filtering process by referring toa table_id field, a version_number field, a section_number field, etc.

As described above, the method of defining the PID of the VCT broadlyincludes two different methods. Herein, the PID of the VCT is a packetidentifier required for identifying the VCT from other tables. The firstmethod consists of setting the PID of the VCT so that it is dependent tothe MGT. In this case, the receiving system cannot directly verify theVCT among the many PSI and/or PSIP tables. Instead, the receiving systemmust check the PID defined in the MGT in order to read the VCT. Herein,the MGT defines the PID, size, version number, and so on, of diversetables. The second method consists of setting the PID of the VCT so thatthe PID is given a base PID value (or a fixed PID value), thereby beingindependent from the MGT. In this case, unlike in the first method, theVCT according to the present invention may be identified without havingto verify every single PID included in the MGT. Evidently, an agreementon the base PID must be previously made between the transmitting systemand the receiving system.

Meanwhile, in the embodiment of the present invention, the demultiplexer703 may output only an application information table (AIT) to the datadecoder 710 by section filtering. The AIT includes information on anapplication being operated in the receiver for the data service. The AITmay also be referred to as an XAIT, and an AMT. Therefore, any tableincluding application information may correspond to the followingdescription. When the AIT is transmitted, a value of ‘0x05’ may beassigned to a stream_type field of the PMT. The AIT may includeapplication information, such as application name, application version,application priority, application ID, application status (i.e.,auto-start, user-specific settings, kill, etc.), application type (i.e.,Java or HTML), position (or location) of stream including applicationclass and data files, application platform directory, and location ofapplication icon.

In the method for detecting application information for the data serviceby using the AIT, component_tag, original_network_id,transport_stream_id, and service_id fields may be used for detecting theapplication information. The component_tag field designates anelementary stream carrying a DSI of a corresponding object carousel. Theoriginal_network_id field indicates a DVB-SI original_network_id of theTS providing transport connection. The transport_stream_id fieldindicates the MPEG TS of the TS providing transport connection, and theservice_id field indicates the DVB-SI of the service providing transportconnection. Information on a specific channel may be obtained by usingthe original_network_id field, the transport_stream_id field, and theservice_id field. The data service data, such as the application data,detected by using the above-described method may be stored in the secondmemory 711 by the data decoder 710.

The data decoder 710 parses the DSM-CC section configuring thedemultiplexed enhanced data. Then, the enhanced data corresponding tothe parsed result are stored as a database in the second memory 711. Thedata decoder 710 groups a plurality of sections having the same tableidentification (table_id) so as to configure a table, which is thenparsed. Thereafter, the parsed result is stored as a database in thesecond memory 711. At this point, by parsing data and/or sections, thedata decoder 710 reads all of the remaining actual section data that arenot section-filtered by the demultiplexer 703. Then, the data decoder710 stores the read data to the second memory 711. The second memory 711corresponds to a table and data carousel database storing systeminformation parsed from tables and enhanced data parsed from the DSM-CCsection. Herein, a table_id field, a section_number field, and alast_section_number field included in the table may be used to indicatewhether the corresponding table is configured of a single section or aplurality of sections. For example, TS packets having the PID of the VCTare grouped to form a section, and sections having table identifiersallocated to the VCT are grouped to form the VCT.

When the VCT is parsed, information on the virtual channel to whichenhanced data are transmitted may be obtained. The obtained applicationidentification information, service component identificationinformation, and service information corresponding to the data servicemay either be stored in the second memory 711 or be outputted to thedata broadcasting application manager 713. In addition, reference may bemade to the application identification information, service componentidentification information, and service information in order to decodethe data service data. Alternatively, such information may also preparethe operation of the application program for the data service.Furthermore, the data decoder 710 controls the demultiplexing of thesystem information table, which corresponds to the information tableassociated with the channel and events. Thereafter, an A.V PID list maybe transmitted to the channel manager 707.

The channel manager 707 may refer to the channel map 708 in order totransmit a request for receiving system-related information data to thedata decoder 710, thereby receiving the corresponding result. Inaddition, the channel manager 707 may also control the channel tuning ofthe tuner 701. Furthermore, the channel manager 707 may directly controlthe demultiplexer 703, so as to set up the A/V PID, thereby controllingthe audio decoder 704 and the video decoder 705. The audio decoder 704and the video decoder 705 may respectively decode and output the audiodata and video data demultiplexed from the main data packet.Alternatively, the audio decoder 704 and the video decoder 705 mayrespectively decode and output the audio data and video datademultiplexed from the enhanced data packet. Meanwhile, when theenhanced data include data service data, and also audio data and videodata, it is apparent that the audio data and video data demultiplexed bythe demultiplexer 703 are respectively decoded by the audio decoder 704and the video decoder 705. For example, an audio-coding (AC)-3 decodingalgorithm may be applied to the audio decoder 704, and a MPEG-2 decodingalgorithm may be applied to the video decoder 705.

Meanwhile, the native TV application manager 706 operates a nativeapplication program stored in the first memory 709, thereby performinggeneral functions such as channel change. The native application programrefers to software stored in the receiving system upon shipping of theproduct. More specifically, when a user request (or command) istransmitted to the receiving system through a user interface (UI), thenative TV application manger 706 displays the user request on a screenthrough a graphic user interface (GUI), thereby responding to the user'srequest. The user interface receives the user request through an inputdevice, such as a remote controller, a key pad, a jog controller, an atouch-screen provided on the screen, and then outputs the received userrequest to the native TV application manager 706 and the databroadcasting application manager 713. Furthermore, the native TVapplication manager 706 controls the channel manager 707, therebycontrolling channel-associated, such as the management of the channelmap 708, and controlling the data decoder 710. The native TV applicationmanager 706 also controls the GUI of the overall receiving system,thereby storing the user request and status of the receiving system inthe first memory 709 and restoring the stored information.

The channel manager 707 controls the tuner 701 and the data decoder 710,so as to managing the channel map 708 so that it can respond to thechannel request made by the user. More specifically, channel manager 707sends a request to the data decoder 710 so that the tables associatedwith the channels that are to be tuned are parsed. The results of theparsed tables are reported to the channel manager 707 by the datadecoder 710. Thereafter, based on the parsed results, the channelmanager 707 updates the channel map 708 and sets up a PID in thedemultiplexer 703 for demultiplexing the tables associated with the dataservice data from the enhanced data.

The system manager 712 controls the booting of the receiving system byturning the power on or off. Then, the system manager 712 stores ROMimages (including downloaded software images) in the first memory 709.More specifically, the first memory 709 stores management programs suchas operating system (OS) programs required for managing the receivingsystem and also application program executing data service functions.The application program is a program processing the data service datastored in the second memory 711 so as to provide the user with the dataservice. If the data service data are stored in the second memory 711,the corresponding data service data are processed by the above-describedapplication program or by other application programs, thereby beingprovided to the user. The management program and application programstored in the first memory 709 may be updated or corrected to a newlydownloaded program. Furthermore, the storage of the stored managementprogram and application program is maintained without being deleted evenif the power of the system is shut down. Therefore, when the power issupplied the programs may be executed without having to be newlydownloaded once again.

The application program for providing data service according to thepresent invention may either be initially stored in the first memory 709upon the shipping of the receiving system, or be stored in the first 709after being downloaded. The application program for the data service(i.e., the data service providing application program) stored in thefirst memory 709 may also be deleted, updated, and corrected.Furthermore, the data service providing application program may bedownloaded and executed along with the data service data each time thedata service data are being received.

When a data service request is transmitted through the user interface,the data broadcasting application manager 713 operates the correspondingapplication program stored in the first memory 709 so as to process therequested data, thereby providing the user with the requested dataservice. And, in order to provide such data service, the databroadcasting application manager 713 supports the graphic user interface(GUI). Herein, the data service may be provided in the form of text (orshort message service (SMS)), voice message, still image, and movingimage. The data broadcasting application manager 713 may be providedwith a platform for executing the application program stored in thefirst memory 709. The platform may be, for example, a Java virtualmachine for executing the Java program. Hereinafter, an example of thedata broadcasting application manager 713 executing the data serviceproviding application program stored in the first memory 709, so as toprocess the data service data stored in the second memory 711, therebyproviding the user with the corresponding data service will now bedescribed in detail.

Assuming that the data service corresponds to a traffic informationservice, the data service according to the present invention is providedto the user of a receiver that is not equipped with an electronic mapand/or a GPS system in the form of at least one of a text (or shortmessage service (SMS)), a voice message, a graphic message, a stillimage, and a moving image. In this case, is a GPS module is mounted onthe receiving system shown in FIG. 9, the GPS module receives satellitesignals transmitted from a plurality of low earth orbit satellites andextracts the current position (or location) information (e.g.,longitude, latitude, altitude), thereby outputting the extractedinformation to the data broadcasting application manager 713.

At this point, it is assumed that the electronic map includinginformation on each link and nod and other diverse graphic informationare stored in one of the second memory 711, the first memory 709, andanother memory that is not shown. More specifically, according to therequest made by the data broadcasting application manager 713, the dataservice data stored in the second memory 711 are read and inputted tothe data broadcasting application manager 713. The data broadcastingapplication manager 713 translates (or deciphers) the data service dataread from the second memory 711, thereby extracting the necessaryinformation according to the contents of the message and/or a controlsignal.

FIG. 10 illustrates a block view showing the structure of a digitalbroadcast (or television) receiver according to another embodiment ofthe present invention. Referring to FIG. 10, the digital broadcastreceiver includes a tuner 801, a demodulating unit 802, a demultiplexer803, a first descrambler 804, an audio decoder 805, a video decoder 806,a second descrambler 807, an authentication unit 808, a native TVapplication manager 809, a channel manager 810, a channel map 811, afirst memory 812, a data decoder 813, a second memory 814, a systemmanager 815, a data broadcasting application manager 816, a storagecontroller 817, a third memory 818, and a telecommunication module 819.Herein, the third memory 818 is a mass storage device, such as a harddisk drive (HDD) or a memory chip. Also, during the description of thedigital broadcast (or television) receiver shown in FIG. 10, thecomponents that are identical to those of the digital broadcast receiverof FIG. 9 will be omitted for simplicity.

As described above, in order to provide services for preventing illegalduplication (or copies) or illegal viewing of the enhanced data and/ormain data that are transmitted by using a broadcast network, and toprovide paid broadcast services, the transmitting system may generallyscramble and transmit the broadcast contents. Therefore, the receivingsystem needs to descrample the scrambled broadcast contents in order toprovide the user with the proper broadcast contents. Furthermore, thereceiving system may generally be processed with an authenticationprocess with an authentication means before the descrambling process.Hereinafter, the receiving system including an authentication means anda descrambling means according to an embodiment of the present inventionwill now be described in detail.

According to the present invention, the receiving system may be providedwith a descrambling means receiving scrambled broadcasting contents andan authentication means authenticating (or verifying) whether thereceiving system is entitled to receive the descrambled contents.Hereinafter, the descrambling means will be referred to as first andsecond descramblers 804 and 807, and the authentication means will bereferred to as an authentication unit 808. Such naming of thecorresponding components is merely exemplary and is not limited to theterms suggested in the description of the present invention. Forexample, the units may also be referred to as a decryptor. Although FIG.10 illustrates an example of the descramblers 804 and 807 and theauthentication unit 808 being provided inside the receiving system, eachof the descramblers 804 and 807 and the authentication unit 808 may alsobe separately provided in an internal or external module. Herein, themodule may include a slot type, such as a SD or CF memory, a memorystick type, a USB type, and so on, and may be detachably fixed to thereceiving system.

As described above, when the authentication process is performedsuccessfully by the authentication unit 808, the scrambled broadcastingcontents are descrambled by the descramblers 804 and 807, thereby beingprovided to the user. At this point, a variety of the authenticationmethod and descrambling method may be used herein. However, an agreementon each corresponding method should be made between the receiving systemand the transmitting system. Hereinafter, the authentication anddescrambling methods will now be described, and the description ofidentical components or process steps will be omitted for simplicity.

The receiving system including the authentication unit 808 and thedescramblers 804 and 807 will now be described in detail. The receivingsystem receives the scrambled broadcasting contents through the tuner801 and the demodulating unit 802. Then, the system manager 815 decideswhether the received broadcasting contents have been scrambled. Herein,the demodulating unit 802 may be included as a demodulating meansaccording to an embodiment of the present invention as described in FIG.11. However, the present invention is not limited to the examples givenin the description set forth herein. If the system manager 815 decidesthat the received broadcasting contents have been scrambled, then thesystem manager 815 controls the system to operate the authenticationunit 808. As described above, the authentication unit 808 performs anauthentication process in order to decide whether the receiving systemaccording to the present invention corresponds to a legitimate hostentitled to receive the paid broadcasting service. Herein, theauthentication process may vary in accordance with the authenticationmethods.

For example, the authentication unit 808 may perform the authenticationprocess by comparing an IP address of an IP datagram within the receivedbroadcasting contents with a specific address of a corresponding host.At this point, the specific address of the corresponding receivingsystem (or host) may be a MAC address. More specifically, theauthentication unit 808 may extract the IP address from the decapsulatedIP datagram, thereby obtaining the receiving system information that ismapped with the IP address. At this point, the receiving system shouldbe provided, in advance, with information (e.g., a table format) thatcan map the IP address and the receiving system information.Accordingly, the authentication unit 808 performs the authenticationprocess by determining the conformity between the address of thecorresponding receiving system and the system information of thereceiving system that is mapped with the IP address. In other words, ifthe authentication unit 808 determines that the two types of informationconform to one another, then the authentication unit 808 determines thatthe receiving system is entitled to receive the correspondingbroadcasting contents.

In another example, standardized identification information is definedin advance by the receiving system and the transmitting system. Then,the identification information of the receiving system requesting thepaid broadcasting service is transmitted by the transmitting system.Thereafter, the receiving system determines whether the receivedidentification information conforms with its own unique identificationnumber, so as to perform the authentication process. More specifically,the transmitting system creates a database for storing theidentification information (or number) of the receiving systemrequesting the paid broadcasting service. Then, if the correspondingbroadcasting contents are scrambled, the transmitting system includesthe identification information in the EMM, which is then transmitted tothe receiving system.

If the corresponding broadcasting contents are scrambled, messages(e.g., entitlement control message (ECM), entitlement management message(EMM)), such as the CAS information, mode information, message positioninformation, that are applied to the scrambling of the broadcastingcontents are transmitted through a corresponding data header or antherdata packet. The ECM may include a control word (CW) used for scramblingthe broadcasting contents. At this point, the control word may beencoded with an authentication key. The EMM may include anauthentication key and entitlement information of the correspondingdata. Herein, the authentication key may be encoded with areceiver-specific distribution key. In other words, assuming that theenhanced data are scrambled by using the control word, and that theauthentication information and the descrambling information aretransmitted from the transmitting system, the transmitting systemencodes the CW with the authentication key and, then, includes theencoded CW in the entitlement control message (ECM), which is thentransmitted to the receiving system. Furthermore, the transmittingsystem includes the authentication key used for encoding the CW and theentitlement to receive data (or services) of the receiving system (i.e.,a standardized serial number of the receiving system that is entitled toreceive the corresponding broadcasting service or data) in theentitlement management message (EMM), which is then transmitted to thereceiving system.

Accordingly, the authentication unit 808 of the receiving systemextracts the identification information of the receiving system and theidentification information included in the EMM of the broadcastingservice that is being received. Then, the authentication unit 808determines whether the identification information conform to each other,so as to perform the authentication process. MOTE specifically, if theauthentication unit 808 determines that the information conform to eachother, then the authentication unit 808 eventually determines that thereceiving system is entitled to receive the request broadcastingservice.

In yet another example, the authentication unit 808 of the receivingsystem may be detachably fixed to an external module. In this case, thereceiving system is interfaced with the external module through a commoninterface (CI). In other words, the external module may receive the datascrambled by the receiving system through the common interface, therebyperforming the descrambling process of the received data. Alternatively,the external module may also transmit only the information required forthe descrambling process to the receiving system. The common interfaceis configured on a physical layer and at least one protocol layer.Herein, in consideration of any possible expansion of the protocol layerin a later process, the corresponding protocol layer may be configuredto have at least one layer that can each provide an independentfunction.

The external module may either consist of a memory or card havinginformation on the key used for the scrambling process and otherauthentication information but not including any descrambling function,or consist of a card having the above-mentioned key information andauthentication information and including the descrambling function. Boththe receiving system and the external module should be authenticated inorder to provide the user with the paid broadcasting service provided(or transmitted) from the transmitting system. Therefore, thetransmitting system can only provide the corresponding paid broadcastingservice to the authenticated pair of receiving system and externalmodule.

Additionally, an authentication process should also be performed betweenthe receiving system and the external module through the commoninterface. More specifically, the module may communicate with the systemmanager 815 included in the receiving system through the commoninterface, thereby authenticating the receiving system. Alternatively,the receiving system may authenticate the module through the commoninterface. Furthermore, during the authentication process, the modulemay extract the unique ID of the receiving system and its own unique IDand transmit the extracted IDs to the transmitting system. Thus, thetransmitting system may use the transmitted ID values as informationdetermining whether to start the requested service or as paymentinformation. Whenever necessary, the system manager 815 transmits thepayment information to the remote transmitting system through thetelecommunication module 819.

The authentication unit 808 authenticates the corresponding receivingsystem and/or the external module. Then, if the authentication processis successfully completed, the authentication unit 808 certifies thecorresponding receiving system and/or the external module as alegitimate system and/or module entitled to receive the requested paidbroadcasting service. In addition, the authentication unit 808 may alsoreceive authentication-associated information from a mobiletelecommunications service provider to which the user of the receivingsystem is subscribed, instead of the transmitting system providing therequested broadcasting service. In this case, theauthentication-association information may either be scrambled by thetransmitting system providing the broadcasting service and, then,transmitted to the user through the mobile telecommunications serviceprovider, or be directly scrambled and transmitted by the mobiletelecommunications service provider. Once the authentication process issuccessfully completed by the authentication unit 808, the receivingsystem may descramble the scrambled broadcasting contents received fromthe transmitting system. At this point, the descrambling process isperformed by the first and second descramblers 804 and 807. Herein, thefirst and second descramblers 804 and 807 may be included in an internalmodule or an external module of the receiving system.

The receiving system is also provided with a common interface forcommunicating with the external module including the first and seconddescramblers 804 and 807, so as to perform the descrambling process.More specifically, the first and second descramblers 804 and 807 may beincluded in the module or in the receiving system in the form ofhardware, middleware or software. Herein, the descramblers 804 and 807may be included in any one of or both of the module and the receivingsystem. If the first and second descramblers 804 and 807 are providedinside the receiving system, it is advantageous to have the transmittingsystem (i.e., at least any one of a service provider and a broadcaststation) scramble the corresponding data using the same scramblingmethod.

Alternatively, if the first and second descramblers 804 and 807 areprovided in the external module, it is advantageous to have eachtransmitting system scramble the corresponding data using differentscrambling methods. In this case, the receiving system is not requiredto be provided with the descrambling algorithm corresponding to eachtransmitting system. Therefore, the structure and size of receivingsystem may be simplified and more compact. Accordingly, in this case,the external module itself may be able to provide CA functions, whichare uniquely and only provided by each transmitting systems, andfunctions related to each service that is to be provided to the user.The common interface enables the various external modules and the systemmanager 815, which is included in the receiving system, to communicatewith one another by a single communication method. Furthermore, sincethe receiving system may be operated by being connected with at leastone or more modules providing different services, the receiving systemmay be connected to a plurality of modules and controllers.

In order to maintain successful communication between the receivingsystem and the external module, the common interface protocol includes afunction of periodically checking the status of the oppositecorrespondent. By using this function, the receiving system and theexternal module is capable of managing the status of each oppositecorrespondent. This function also reports the user or the transmittingsystem of any malfunction that may occur in any one of the receivingsystem and the external module and attempts the recovery of themalfunction.

In yet another example, the authentication process may be performedthrough software. More specifically, when a memory card having CASsoftware downloaded, for example, and stored therein in advanced isinserted in the receiving system, the receiving system receives andloads the CAS software from the memory card so as to perform theauthentication process. In this example, the CAS software is read outfrom the memory card and stored in the first memory 812 of the receivingsystem. Thereafter, the CAS software is operated in the receiving systemas an application program. According to an embodiment of the presentinvention, the CAS software is mounted on for stored) in a middlewareplatform and, then executed. A Java middleware will be given as anexample of the middleware included in the present invention. Herein, theCAS software should at least include information required for theauthentication process and also information required for thedescrambling process.

Therefore, the authentication unit 808 performs authentication processesbetween the transmitting system and the receiving system and alsobetween the receiving system and the memory card. At this point, asdescribed above, the memory card should be entitled to receive thecorresponding data and should include information on a normal receivingsystem that can be authenticated. For example, information on thereceiving system may include a unique number, such as a standardizedserial number of the corresponding receiving system. Accordingly, theauthentication unit 808 compares the standardized serial number includedin the memory card with the unique information of the receiving system,thereby performing the authentication process between the receivingsystem and the memory card.

If the CAS software is first executed in the Java middleware base, thenthe authentication between the receiving system and the memory card isperformed. For example, when the unique number of the receiving systemstored in the memory card conforms to the unique number of the receivingsystem read from the system manager 815, then the memory card isverified and determined to be a normal memory card that may be used inthe receiving system. At this point, the CAS software may either beinstalled in the first memory 812 upon the shipping of the presentinvention, or be downloaded to the first memory 812 from thetransmitting system or the module or memory card, as described above.Herein, the descrambling function may be operated by the databroadcasting application manger 816 as an application program.

Thereafter, the CAS software parses the EMM/ECM packets outputted fromthe demultiplexer 803, so as to verify whether the receiving system isentitled to receive the corresponding data, thereby obtaining theinformation required for descrambling (i.e., the CW) and providing theobtained CW to the descramblers 804 and 807. More specifically, the CASsoftware operating in the Java middleware platform first reads out theunique (or serial) number of the receiving system from the correspondingreceiving system and compares it with the unique number of the receivingsystem transmitted through the EMM, thereby verifying whether thereceiving system is entitled to receive the corresponding data. Once thereceiving entitlement of the receiving system is verified, thecorresponding broadcasting service information transmitted to the ECMand the entitlement of receiving the corresponding broadcasting serviceare used to verify whether the receiving system is entitled to receivethe corresponding broadcasting service. Once the receiving system isverified to be entitled to receive the corresponding broadcastingservice, the authentication key transmitted to the EMM is used to decode(or decipher) the encoded CW, which is transmitted to the ECM, therebytransmitting the decoded CW to the descramblers 804 and 807. Each of thedescramblers 804 and 807 uses the CW to descramble the broadcastingservice.

Meanwhile, the CAS software stored in the memory card may be expanded inaccordance with the paid service which the broadcast station is toprovide. Additionally, the CAS software may also include otheradditional information other than the information associated with theauthentication and descrambling. Furthermore, the receiving system maydownload the CAS software from the transmitting system so as to upgrade(or update) the CAS software originally stored in the memory card. Asdescribed above, regardless of the type of broadcast receiver, as longas an external memory interface is provided, the present invention mayembody a CAS system that can meet the requirements of all types ofmemory card that may be detachably fixed to the receiving system. Thus,the present invention may realize maximum performance of the receivingsystem with minimum fabrication cost, wherein the receiving system mayreceive paid broadcasting contents such as broadcast programs, therebyacknowledging and regarding the variety of the receiving system.Moreover, since only the minimum application program interface isrequired to be embodied in the embodiment of the present invention, thefabrication cost may be minimized, thereby eliminating themanufacturer's dependence on CAS manufacturers. Accordingly, fabricationcosts of CAS equipments and management systems may also be minimized.

Meanwhile, the descramblers 804 and 807 may be included in the moduleeither in the form of hardware or in the form of software. In this case,the scrambled data that being received are descrambled by the module andthen demodulated. Also, if the scrambled data that are being receivedare stored in the third memory 818, the received data may be descrambledand then stored, or stored in the memory at the point of being receivedand then descrambled later on prior to being played (or reproduced).Thereafter, in case scramble/descramble algorithms are provided in thestorage controller 817, the storage controller 817 scrambles the datathat are being received once again and then stores the re-scrambled datato the third memory 818.

In yet another example, the descrambled broadcasting contents(transmission of which being restricted) are transmitted through thebroadcasting network. Also, information associated with theauthentication and descrambling of data in order to disable thereceiving restrictions of the corresponding data are transmitted and/orreceived through the telecommunications module 819. Thus, the receivingsystem is able to perform reciprocal (or two-way) communication. Thereceiving system may either transmit data to the telecommunicationmodule within the transmitting system or be provided with the data fromthe telecommunication module within the transmitting system. Herein, thedata correspond to broadcasting data that are desired to be transmittedto or from the transmitting system, and also unique information (i.e.,identification information) such as a serial number of the receivingsystem or MAC address.

The telecommunication module 819 included in the receiving systemprovides a protocol required for performing reciprocal (or two-way)communication between the receiving system, which does not support thereciprocal communication function, and the telecommunication moduleincluded in the transmitting system. Furthermore, the receiving systemconfigures a protocol data unit (PDU) using a tag-length-value (TLV)coding method including the data that are to be transmitted and theunique information (or ID information). Herein, the tag field includesindexing of the corresponding PDU. The length field includes the lengthof the value field. And, the value field includes the actual data thatare to be transmitted and the unique number (e.g., identificationnumber) of the receiving system.

The receiving system may configure a platform that is equipped with theJava platform and that is operated after downloading the Javaapplication of the transmitting system to the receiving system throughthe network. In this case, a structure of downloading the PDU includingthe tag field arbitrarily defined by the transmitting system from astorage means included in the receiving system and then transmitting thedownloaded PDU to the telecommunication module 819 may also beconfigured. Also, the PDU may be configured in the Java application ofthe receiving system and then outputted to the telecommunication module819. The PDU may also be configured by transmitting the tag value, theactual data that are to be transmitted, the unique information of thecorresponding receiving system from the Java application and byperforming the TLV coding process in the receiving system. Thisstructure is advantageous in that the firmware of the receiving systemis not required to be changed even if the data (or application) desiredby the transmitting system is added.

The telecommunication module within the transmitting system eithertransmits the PDU received from the receiving system through a wirelessdata network or configures the data received through the network into aPDU which is transmitted to the host. At this point, when configuringthe PDU that is to be transmitted to the host, the telecommunicationmodule within the transmitting end may include unique information (e.g.,IP address) of the transmitting system which is located in a remotelocation. Additionally, in receiving and transmitting data through thewireless data network, the receiving system may be provided with acommon interface, and also provided with a WAP, CDMA 1x EV-DO, which canbe connected through a mobile telecommunication base station, such asCDMA and GSM, and also provided with a wireless LAN, mobile Internet,WiBro, WiMax, which can be connected through an access point. Theabove-described receiving system corresponds to the system that is notequipped with a telecommunication function. However, a receiving systemequipped with telecommunication function does not require thetelecommunication module 819.

The broadcasting data being transmitted and received through theabove-described wireless data network may include data required forperforming the function of limiting data reception. Meanwhile, thedemultiplexer 803 receives either the real-time data outputted from thedemodulating unit 802 or the data read from the third memory 818,thereby performing demultiplexing. In this embodiment of the presentinvention, the demultiplexer 803 performs demultiplexing on the enhanceddata packet. Similar process steps have already been described earlierin the description of the present invention. Therefore, a detailed ofthe process of demultiplexing the enhanced data will be omitted forsimplicity.

The first descrambler 804 receives the demultiplexed signals from thedemultiplexer 803 and then descrambles the received signals. At thispoint, the first descrambler 804 may receive the authentication resultreceived from the authentication unit 808 and other data required forthe descrambling process, so as to perform the descrambling process. Theaudio decoder 805 and the video decoder 806 receive the signalsdescrambled by the first descrambler 804, which are then decoded andoutputted. Alternatively, if the first descrambler 804 did not performthe descrambling process, then the audio decoder 805 and the videodecoder 806 directly decode and output the received signals. In thiscase, the decoded signals are received and then descrambled by thesecond descrambler 807 and processed accordingly.

As described above, the DTV transmitter and receiver, and dataprocessing method according to the present invention have the followingadvantages. More specifically, the digital broadcasttransmitting/receiving system and data processing method according tothe present invention is highly protected against (or resistant to) anyerror that may occur when transmitting supplemental data through achannel. And, the present invention is also highly compatible to theconventional VSB receiving system. Moreover, the present invention mayalso receive the supplemental data without any error even in channelshaving severe ghost effect and noise.

Additionally, by inserting known data in a specific place (or position)of the data domain and transmitting the processed data, the receivingperformance of the digital broadcast (or digital television) receivingsystem liable to a frequent change in channel may be enhanced. Thepresent invention is even more effective when applied to mobile andportable receivers, which are also liable to a frequent change inchannel and which require protection (or resistance) against intensenoise. Furthermore, by regularly inserting and transmitting known datahaving identical patterns to the valid data, and by having the receivingend perform channel equalization in a circular convolution form, thestructure of the channel equalizer is simplified, thereby enhancing theequalization performance.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A digital television (DTV) receiver comprising: a tuner for receivinga broadcast signal including main data, enhanced data and known datasymbol sequences, wherein the main data and the enhanced data areinterleaved, wherein at least two of the known data symbol sequences areregularly spaced in the interleaved main data and enhanced data of thereceived broadcast signal, and wherein at least one known data symbolsequence has a repeated pattern; a demodulator for demodulating thereceived broadcast signal by performing carrier recovery on the receivedbroadcast signal based on the repeated pattern of the at least one knowndata symbol sequence; a channel equalizer for estimating a channelimpulse response based on the known data symbol sequences which areregularly spaced in the interleaved main data and enhanced data of thedemodulated broadcast signal and compensating channel distortion of thedemodulated broadcast signal based on the estimated channel impulseresponse; a deinterleaver for deinterleaving the enhanced data in thecompensated broadcast signal; a Reed-Solomon (RS) decoder for RSdecoding the deinterleaved enhanced data; and a derandomizer forderandomizing the RS-decoded enhanced data.
 2. The DTV receiver of claim1, wherein the channel equalizer comprises: a first transformer forconverting the demodulated broadcast signal into first frequency domaindata; a channel estimator for estimating a channel impulse responseusing the known data symbol sequences which are regularly spaced in theinterleaved main data and enhanced data of the first frequency domaindata; a second transformer for converting the estimated channel impulseresponse into second frequency domain data; a calculator for calculatingequalization coefficients based on the second frequency domain data; acompensator for compensating channel distortion of the first frequencydomain data by multiplying the first frequency domain data with theequalization coefficients; and a third transformer for converting thecompensated first frequency domain data into time domain data.
 3. TheDTV receiver of claim 2, wherein the first transformer converts thedemodulated broadcast signal into the first frequency domain data usinga fast Fourier transform (FFT).
 4. The DTV receiver of claim 2, whereinthe second transformer converts the estimated channel impulse responseinto the second frequency domain data using a fast Fourier transform(FFT).
 5. The DTV receiver of claim 2, wherein the third transformerconverts the compensated first frequency domain data into the timedomain data using an inverse fast Fourier transform (IFFT).
 6. A methodof processing broadcast data in a digital television (DTV) receiver, themethod comprising: receiving, by a tuner, a broadcast signal includingmain data, enhanced data and known data symbol sequences, wherein themain data and the enhanced data are interleaved, wherein at least two ofthe known data symbol sequences are regularly spaced in the interleavedmain data and enhanced data of the received broadcast signal, andwherein at least one known data symbol sequence has a repeated pattern;demodulating, by a demodulator, the received broadcast signal byperforming carrier recovery on the received broadcast signal based onthe repeated pattern of the at least one known data symbol sequence;estimating, by a channel equalizer, a channel impulse response based onthe known data symbol sequences which are regularly spaced in theinterleaved main data and enhanced data in the demodulated broadcastsignal and compensating channel distortion of the demodulated broadcastsignal based on the estimated channel impulse response; deinterleaving,by a deinterleaver, the enhanced data in the compensated broadcastsignal; Reed-Solomon (RS) decoding, by an RS decoder, the deinterleavedenhanced data; and derandomizing, by a derandomizer, the RS-decodedenhanced data.
 7. The method of claim 6, wherein the channel equalizercomprises: a first transformer for converting the demodulated broadcastsignal into first frequency domain data; a channel estimator forestimating a channel impulse response using the known data symbolsequences which are regularly spaced in the interleaved main data andenhanced data of the first frequency domain data; a second transformerfor converting the estimated channel impulse response into secondfrequency domain data; a calculator for calculating equalizationcoefficients based on the second frequency domain data; a compensatorfor compensating channel distortion of the first frequency domain databy multiplying the first frequency domain data with the equalizationcoefficients; and a third transformer for converting the compensatedfirst frequency domain data into time domain data.
 8. The method ofclaim 7, wherein the first transformer converts the demodulatedbroadcast signal into the first frequency domain data using a fastFourier transform (FFT).
 9. The method of claim 7, wherein the secondtransformer converts the estimated channel impulse response into thesecond frequency domain data using a fast Fourier transform (FFT). 10.The method of claim 7, wherein the third transformer converts thecompensated first frequency domain data into the time domain data usingan inverse fast Fourier transform (IFFT).